The common carp and other scavenger fish have become ubiquitous in many rivers and streams. Their habits of “rooting” and benthic (e.g., bottom) feeding often cause high turbidity levels, increased concentrations of suspended solids, destruction of emergent aquatic plants, as well as excessive competition with native fish species. Consequently, in many streams and rivers where carp are abundant, the water quality decreases as does the population of native fish.
Carp densities, however, are difficult to control. Conventional efforts to control carp have been based primarily on removal and poisoning techniques, largely with ineffectual and sometimes detrimental results. Carp quickly re-invade areas from which they have been removed, and many of the poisons are not specific or effective enough to eliminate the carp while allowing the native fish species to survive. Thus, large and growing populations of carp remain a detriment to the health of many rivers and streams.
Carp can be particularly damaging to aquatic plants. Disruption of the soft substrates on stream and lake bottoms as a result of feeding by carp dislodges or harms many aquatic plants. Additionally, the increased turbidity caused by the disruption of bottom substrates decreases the ability of light to penetrate water, which reduces plant reproduction and viability. Consequently, the presence of carp is likely to decrease the success of attempts to re-establish aquatic plants in areas where the plants were once abundant.